The field of the invention is camera cranes.
Camera cranes are used in the production of motion pictures, video, and television programs. Typically, a camera crane arm or boom is pivotably mounted onto a base, such as a mobile dolly or platform. A camera is mounted on a camera platform at the front end of the arm. Counterweights on a counterweight platform at the back end of the arm are added to try to keep the arm into a balanced, or near balanced equilibrium.
With certain crane arms, it may be difficult to adequately balance the arm by placing counterweights at the back end. The counterweights are generally provided in selected incremental weight increments, such as 50 and 100 pound weights. Accordingly, with some crane arms and payloads, the precise amount of weight on the back end cannot be readily achieved. The crane arm may also not react under load as a perfectly straight lever. The arm necessarily also deflects or sags under load. Some payloads may have eccentric force components or torque elements. Friction forces may also vary. For these and other reasons, balancing the crane arm by placing counterweights at the back end of the arm may be difficult. If the arm is not balanced, it must be held in place with a brake. However, moving the unbalanced arm into any desired position then requires greater lifting force by the crane operator. As a result, crane arm movement is generally slower, and achieving precise camera positioning becomes more difficult. Accordingly, engineering challenges remain in the design of crane arm balancing systems.